Mobile communication networks are ubiquitous in many parts of the world. Third- and fourth-generation mobile networks utilize Radio Frequency (RF) transmissions in a Radio Access Network (RAN) to effect voice and data communications between geographically dispersed network nodes (Base Stations or BSs) and a large number of mobile communication terminals (Mobile Terminals, or MTs). Radio Resource Allocation (RRA) algorithms are responsible for the management of the scarce resources available in the RAN. Efficient RRA is critical since the limited resources must be shared by numerous communication links in the mobile networks. If the radio resources are used efficiently, more communication links can be provided by the mobile network, increasing capacity and thus generating more operating revenue for a given fixed network infrastructure investment.
Since RRA manages the available radio resources, system aspects that restrict the use of these resources have a direct impact on the RRA design. Among these system aspects that must be considered are the multiple access schemes, power budgets on BSs and MTs, signaling load limitations, and many others.
The 3rd Generation Partnership Project (3GPP), a wireless communication standards body, has chosen Single Carrier—Frequency Division Multiple Access (SC-FDMA) as the multiple access technology for the uplink of Long Term Evolution (LTE) networks. One reason for adopting SC-FDMA is its property of controlling Peak-to-Average Power Ratio (PAPR). Signals with high PAPR place a significant burden on MTs, due to the need for highly linear power amplifiers to avoid excessive signal distortion. For more information, see the paper by H. G. Myung, J. Lim, and D. J. Goodman, titled “Single Carrier FDMA for Uplink Wireless Transmission,” published in IEEE Vehicular Technology Magazine, vol. 1, no. 3, pp. 30-38, September 2006, the disclosure of which is incorporated herein by reference in its entirety.
The SC-FDMA multiple access scheme imposes two constraints on resource assignment: exclusivity and adjacency. With the exclusivity constraint, a given frequency resource, such as an OFDM subcarrier or set of frequency-adjacent OFDM subcarriers, should not be shared by multiple MTs within a cell. In other words, each frequency resource should be assigned to at most one MT within a cell to prevent intra-cell interference. In the adjacency constraint, the frequency resource blocks allocated to a given MT for transmission—i.e., a set of two or more frequency resources—should be adjacent to each other in the frequency domain, so as to obtain benefits in terms of PAPR. The adjacency constraint significantly reduces the freedom in RRA compared to other multiple access schemes.
Optimized and efficient RRA leads to improved utilization of scarce radio resources. In practical terms, improved resource utilization means the transmission of more bits per radio resource. A typical system capacity metric is the number of transmitted bits per time and frequency resource. Accordingly, one standing challenge in modern mobile communication network design is performing RRA so as to improve the resource usage/capacity in the SC-FDMA uplink. Several theoretical or computationally complex approaches to this task are known in the art. However, a significant practical constraint, lacking in prior art solutions, is that RRA optimization should be possible with affordable computational complexity. This means that a RRA method or algorithm must be able to solve the resource allocation problem within the short time period required by scheduling tasks in mobile networks. Prior art approaches to SC-FDMA uplink RRA do not achieve sufficiently affordable computational complexity to be useful in real-world mobile networks.
The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.